New rendering: Move the article lead image

[romu70]

⚠️ If your issue is about an error during fetching a link, please read: http://doc.wallabag.org/en/user/errors_during_fetching.html#how-can-i-help-to-fix-that

Issue details

New rendering improvement.

When the article has a lead image, it should be placed in the first place, so before the H1. In my testing, I took the "header" section which contains the lead image and moved to between the div with the "article" ID and the header with the "mbm" class.

But feel free to do it differently ;)

Environment

• wallabag version (or git revision) that exhibits the issue:
• How did you install wallabag? Via git clone or by downloading the package?
• Last wallabag version that did not exhibit the issue (if applicable):
• php version:
• OS:
• type of hosting (shared or dedicated):
• which storage system you choose at install (SQLite, MySQL/MariaDB or PostgreSQL):

Steps to reproduce/test case

Please provide necessary steps for reproduction of this issue, or better the
reduced test case (without any external dependencies, if possible).